It is possible that an ink made by dispersing or dissolving a sublimation dye into a resinous liquid is coated and dried on a paper to form a dye carrier ribbon, this dye carrier ribbon is heated on its back surface by a thermal print head to sublimate the dye contained in the ink, and the dye then is transferred to a suitably surface treated printing paper which is suitably to be superposed to the dye carrier paper, whereby a color copy can be obtained. In this case, since in general a temperature of the thermal print head reaches 200.degree. C. or above, a resin in the dye carrier ribbon (hereinafter referred to as a binder) and a resin which is coated in the surface treating layer of the printing paper are both softened by heat and then adhered to each other by melt. To avoid this, the binder and the coating resin are cross-linked so as to have a heat resisting property. This, however, could not achieve satisfactory effect.
As the resin used in a coating composition which is coated on the surface of the printing paper, there is used a thermo-plastic resin, for example, saturated linear polyester resin, epoxy resin and the like which can excellently adsorb and diffuse a sublimation dye.
Since these resins are melted or softened inherently by heat generated from a thermal print head and the sublimated dye is effectively transferred and diffused on that portion so as to be colored, these resins are apt to be adhered by melt with the binder contained in the dye carrier ribbon. To solve this problem, it has been done to improve the heat resisting property of the coating resin by cross-linking made by addition reaction using isocyanate group and the like, or cross-linking made by condensation reaction using melamine resin or the like. This could not provide a satisfactory heat resisting property so that the adherence by melt could not be avoided. On the other hand, a coating layer having excellent heat resisting property was provided by the cross-linking using the amine-series curing agent of epoxy resin. This coating layer could not be prevented from being adhered by melt with the dye carrier ribbon.